Paper tray unit

ABSTRACT

A paper tray unit includes a paper size sensor which is attached to a paper tray and determines a paper size in a paper width direction by detecting a position of a paper width guide. In the paper tray unit, a movable member moves in a paper feed direction accompanying movement of the paper width guide. The position of the paper width guide is detected by the paper size sensor detecting or not detecting the movable member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a paper tray unit on which a paper isplaced to be fed into a paper transportation path. In particular, thepresent invention relates to a paper tray unit including a paper widthguide, which is movably mounted on an upper surface of the paper trayunit in a direction that is substantially perpendicular to a paper feeddirection and positions a paper in a paper width direction, and a papersize sensor, which is provided on a reverse surface of the paper trayunit and determines a paper size in the paper width direction bydetecting a position of the paper width guide.

2. Description of the Related Art

Many scanners, facsimiles, and copiers or the like have an imagescanning device for scanning image information of an original document.One image scanning method used in the image scanning device is a sheetthrough method, which scans an image by sequentially transporting aplurality of original documents. The sheet through method is mainly usedby an Automatic Document Feeder (ADF). FIG. 8 is a schematiclongitudinal sectional view of a conventional image scanning device 70accommodating the ADF. As illustrated in FIG. 8, the image scanningdevice 70 includes an original document tray unit 71, a paper dischargetray 72, and an ADF 73. An original document 101 to be scanned is placedon the original document tray unit 71. The paper discharge tray 72 isprovided directly under the original document tray unit 71. The ADF 73transports the original document 101 from the original document trayunit 71 onto the paper discharge tray 72. In the image scanning device70, the original documents 101 stacked on the original document trayunit 71 are separated one sheet at a time from an uppermost sheet by apaper feed unit 74, which defines the ADF 73, and each original document101 is transported from a paper feed port 75 into an original documenttransportation path 76. After image information is scanned at aprescribed position in the original document transportation path 76, theoriginal document 101 is discharged from a paper discharge port 77 ontothe paper discharge tray 72.

As illustrated in FIG. 8, the original document tray unit 71 includes anoriginal document tray 78, a pair of right and left original documentwidth guides 79, a pinion gear 80, a pair of rack members 81, and papersize sensors 82. The original document 101 is placed on the originaldocument tray 78. The pair of the right and left original document widthguides 79 is slidable in a direction orthogonal to a paper feeddirection 100, which is shown by an outlined arrow in FIG. 8, on anupper surface of the original document tray 78. The pair of the rightand left original document width guides 79 positions the originaldocument 101 in a paper width direction. The pinion gear 80 is rotatablysupported on a reverse surface of the original document tray 78. Therack members 81 are respectively integrated with each of the originaldocument width guides 79 and are meshed with the pinion gear 80. Thepaper size sensor 82 is provided on the reverse surface of the originaldocument tray 78 and determines a size of the original document 101 inthe paper width direction. In the above-described structure, when one ofthe original document width guides 79 slides, the other originaldocument width guide 79 slides in an opposite direction accordingly.

FIG. 9 is an enlarged schematic perspective view of the paper sizesensor 82. In the paper size sensor 82, a light-emitting element 83,which emits a light beam, and a light-receiving element 84, whichdetects the emitted light beam, are arranged to face one another acrossa detection groove 85. The paper size sensor 82 is a transmissiveoptical sensor which detects a passage of an object when light isblocked. The paper size sensor 82 has a height dimension H that islarger than a depth dimension D, and is provided with four snap-fits 86at a base end portion of the paper size sensor 82 for attaching thepaper size sensor 82 to the reverse surface of the original documenttray 78. As illustrated in FIG. 8, two of the paper size sensors 82 arearranged in the original document tray unit 71 such that a heightdirection of the paper size sensor 82 extends in a height direction ofthe original document tray unit 71. Each of the paper size sensors 82detects a position of each of the original document width guides 79 bydetecting or not detecting a rib 87 protruding from each of the rackmembers 81. Accordingly, a paper size of the original document 101 inthe paper width direction can be determined.

However, because of a structure of the conventional original documenttray unit 71, the height dimension of the entire ADF 73 increases.Specifically, since the paper size sensor 82 is attached to the originaldocument tray 78 such that the height direction of the paper size sensor82, which is a direction in which the dimension of the paper size sensor82 is large, extends in the height direction of the original documenttray unit 71, a height dimension of the original document tray unit 71increases as a whole. Meanwhile, the paper discharge port 77 provideddirectly under the original document tray unit 71 is required to bepositioned at a certain height above the paper discharge tray 72. Thatis, if a leading edge of the original document 101 touches the paperdischarge tray 72 before the original document 101 is completelydischarged from the paper discharge port 77, friction is generatedbetween the original document 101 and the paper discharge tray 72,causing a state in which the original document 101 stops without beingdropped onto the paper discharge tray 72. In such a state, the nextoriginal document 101 may discharge underneath the stopped originaldocument 101, changing an order of the original documents 101, or apaper jam may occur. In order to prevent such problems, an end portionof the original document transportation path 76 is sloped upward,positioning the paper discharge port 77 at a certain height above thepaper discharge tray 72. Accordingly, the original document 101 iscompletely discharged from the paper discharge port 77 before theleading edge of the original document 101 touches the paper dischargetray 72. In the above-described structure of the ADF 73 and the originaldocument tray unit 71, a certain height is required between the paperfeed port 75 and the paper discharge port 77 so that the originaldocument 101 discharged from the paper discharge port 77 does not touchthe paper size sensor 82. Accordingly, the height dimension of theentire ADF 73 increases, which is not preferable in terms of savingspace.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a structure for preventing a dischargedoriginal document from touching an original document tray unit, withoutrequiring a large height dimension to be provided between a paper feedport and a paper discharge port by minimizing a height of the originaldocument tray unit.

According to a preferred embodiment of the present invention, a papertray unit includes a paper tray, a paper width guide, and a paper sizesensor. A paper to be fed into a paper transportation path is placed onthe paper tray. A paper discharge port of the paper transportation pathis provided directly under the paper tray. The paper width guide isarranged on an upper surface of the paper tray to be movable in adirection that is substantially perpendicular to a paper feed directionand determines a position of the paper in a paper width direction. Thepaper size sensor is attached to a reverse surface of the paper tray anddetermines a size of the paper in the paper width direction by detectinga position of the paper width guide. In the above-described paper tray,a movable member, which moves in the paper feed direction accompanyingmovement of the paper width guide, is provided, and a position of thepaper width guide is detected by the paper size sensor by detecting ornot detecting the movable member.

According to another preferred embodiment of the present invention, inthe paper tray unit, a height of the paper size sensor protruding from areverse surface of the paper tray is within a range in which the paperdischarged from the paper discharge port does not touch the paper sizesensor.

According to another preferred embodiment of the present invention, inthe paper tray unit, the paper size sensor is a transmissive opticalsensor which emits a light beam across a detection groove. Further, themovable member passes through the detection groove.

According to another preferred embodiment of the present invention, inthe paper tray unit, the paper size sensor has the largest dimension ina height direction of the detection groove and is attached such that theheight direction of the detection groove is substantially parallel tothe paper tray unit.

According to each of the above-described preferred embodiments of thepresent invention, in the paper tray unit, the movable member moves inthe paper feed direction accompanying the movement of the paper widthguide. A paper size in a paper width direction can be determined by thepaper size sensor by detecting the movable member. Thus, the paper sizesensor can be attached such that a depth direction of the paper sizesensor, which has a small dimension, extends in a height direction ofthe paper tray unit. As a result, a height of the entire paper tray unitcan be reduced, and even without providing a long distance between thepaper feed port and the paper discharge port, a paper discharged fromthe paper discharge port can be prevented from touching the paper trayunit. Accordingly, the height dimension of the entire device can bereduced, and space can be saved.

Other features, elements, processes, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view illustrating an exterior of animage scanning device including an original document tray unit accordingto a first preferred embodiment of the present invention.

FIG. 2 is a schematic plan view illustrating a structure of a reversesurface of an original document tray unit.

FIG. 3 is a schematic plan view illustrating a structure of the reversesurface of the original document tray unit.

FIG. 4 is a schematic plan view illustrating a structure of the reversesurface of the original document tray unit.

FIG. 5 is a schematic plan view illustrating a structure of the reversesurface of the original document tray unit.

FIG. 6 is a schematic perspective view illustrating an attachment stateof a rack member, a movable member, a pinion gear, and a paper sizesensor.

FIG. 7 is a schematic plan view illustrating a structure of a reversesurface of an original document tray unit according to a secondpreferred embodiment of the present invention.

FIG. 8 is a schematic perspective view illustrating a reverse surface ofan original document tray unit according to a conventional art.

FIG. 9 is a schematic perspective view illustrating an exterior of apaper size sensor according to a conventional art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Description will be made of an original document tray unit according topreferred embodiments of the present invention with reference to thedrawings. FIG. 1 is a schematic perspective view illustrating anexterior of an image scanning device 200 including an original documenttray unit 1 according to a first preferred embodiment of the presentinvention. The image scanning device 200 is mounted on an upper portionof a copy-and-facsimile multi function peripheral or the like, and isused to scan image information of an original document to be copied orto be transmitted by facsimile. The image scanning device 200 includes adevice main body 2, an ADF 3, an original document tray unit (a papertray unit) 1, a paper discharge tray 4, and an operation panel 5. Thedevice main body 2 accommodates an image scanning unit (not illustrated)inside a hollow chassis. The ADF 3 is provided on an upper surface ofthe device main body 2. The original document (a paper) to be scanned isplaced on the original document tray unit 1. The scanned originaldocument is discharged to the paper discharge tray 4. The operationpanel 5 is provided on a front surface of the device main body 2 and isused to operate the image scanning device 200.

In the image scanning device 200, when a user issues a start command fora scanning operation by operating the operation panel 5, the originaldocuments stacked on the original document tray unit 1 are picked up onesheet at a time from an uppermost sheet and fed into the ADF 3. Theoriginal document is then transported along an original documenttransportation path (a paper transportation path) in the ADF 3, and theimage information of the original document is scanned at a prescribedposition in the original document transportation path by the imagescanning unit. The scanned original document is transported furtherdownstream through the original document transportation path anddischarged onto the paper discharge tray 4 from the paper discharge port(not illustrated) provided directly under the original document trayunit 1.

FIGS. 2 and 5 are schematic plan views illustrating the structure of areverse surface of the original document tray unit 1. As illustrated inFIGS. 1 and 2, the original document tray unit 1 includes an originaldocument tray 6, a pair of right and left paper width guides 7, a piniongear 8, a pair of rack members 9A and 9B, a pair of movable members 10Aand 10B, and a pair of paper size sensors 11. The original document tray6 is a paper tray on which the original document is stacked. The pair ofthe right and left paper width guides 7 is provided on an upper surfaceof the original document tray 6, on which the original document isplaced. The paper width guides 7 position the original document in apaper width direction. The pinion gear 8 is rotatably supported on areverse surface of the original document tray 6. The rack members 9A and9B are respectively integrated with the original document width guides7, and are meshed with the pinion gear 8. The pair of the movablemembers 10A and 10B moves in a direction that is substantiallyperpendicular to a moving direction of the rack members 9A and 9B inresponse to movement of the rack members 9A and 9B. The paper sizesensors respectively detect the movable members 10A and 10B.

The original document tray 6 is a flat plate member that is made ofplastic, resin etc. As illustrated in FIG. 1, in order to reducefriction by reducing a contact area between the original document tray 6and the placed original document, a plurality of ribs 12 are arranged toprotrude from the upper surface of the original document tray 6 andextending in a paper feed direction 100 shown by an outlined arrow. Asillustrated in FIGS. 1 and 2, two elongated holes 13 are formedpenetrating through the original document tray 6 and extend in adirection that is substantially perpendicular to the paper feeddirection 100. The elongated holes 13 are provided at prescribedintervals in the paper feed direction 100. In addition, positionadjustment scales 14 for adjusting a position of the original documentwidth guides 7 are displayed on the upper surface of the originaldocument tray 6 with prescribed intervals between each of the positionadjustment scales 14 in a direction that is substantially perpendicularto the paper feed direction 100. The position adjustment scales 14 aresymmetrically provided with respect to a center of the original documenttray 6 so as to correspond to each of the original document width guides7. Each distance between the corresponding position adjustment scales 14is equal to a width of a standard sized paper. In the present preferredembodiment, paper sizes “B5”, “A4”, “B4”, and “A3” according to theJapanese Industrial Standards (JIS) are sequentially displayed outwardfrom the center of the original document tray 6. Both the number and theinterval of the position adjustment scales 14 can be changed accordingto a type of corresponding paper sizes. In addition, for convenience ofdescription, the position adjustment scales 14 to be displayed on theupper surface of the original document tray 6 are shown on the reversesurface of the original document tray 6 in each drawing. As illustratedin FIG. 2, on the reverse surface of the original document tray 6, guideribs 15 for guiding the rack members 9A and 9B are provided extending ina direction that is substantially perpendicular to the paper feeddirection 100.

As illustrated in FIG. 1, the pair of the original document width guides7 is substantially L-shaped in its longitudinal cross-section. Each ofthe original document width guides 7 includes a contact portion 16,which makes contact with the upper surface of the original document tray6, and a standing portion 17, which projects from one side of thecontact portion 16 and controls one side edge of the original documentin a paper width direction. Each of the original document width guides 7is provided slidably in a direction that is substantially perpendicularto the paper feed direction 100 on the original document tray 6. Inother words, as illustrated in FIG. 2, each of the original documentwidth guides 7 is respectively integrated with each of the rack members9A and 9B via a connecting member 18, and can slide within an area wherethe connecting member 18 is guided along the elongated holes 13 of theoriginal document tray 6. Therefore, as illustrated in FIGS. 2 and 5, bysliding each of the original document width guides 7 according to a sizeof the original document to be scanned, and by adjusting each inner wallsurface of the standing portion 17 respectively to a correspondingposition adjustment scale 14, a distance between the standing portions17 of the original document width guides 7 can conform with the size ofthe original document. In the present preferred embodiment, a pair ofthe original document width guides 7 is preferably provided, and both ofthe original document width guides 7 are slidable. However, the presentinvention is not limited to such an example. For example, a slidableoriginal document width guide 7 may be provided only at one side in awidth direction of the original document, and a positioning wall member(not shown) or the like may be fixedly provided on the other side in thewidth direction of the original document. Accordingly, by sliding theoriginal document width guide 7, both sides of the original document inthe width direction can be positioned.

As illustrated in FIG. 6, the pinion gear 8 includes a gear main body 20having a teethed portion 19 disposed around a circumference of acylinder member, and a substantially disk-shaped flange 21 protruding ina radial direction of the gear main body 20 located at one end of thegear main body 20. The pinion gear 8 also includes a boss inserting hole22 penetrating through the gear main body 20 and the flange 21.

As illustrated in FIG. 6, the rack members 9A and 9B includelongitudinal flat plate members having a teethed portion 23 at one sideof the flat plate member in a width direction. A guide groove 24 isprovided on each of the rack members 9A and 9B extending along alongitudinal direction thereof. The guide groove 24 is substantiallysemicircular in its longitudinal cross-section, and as illustrated inFIG. 2, the guide groove 24 of each of the rack members 9A and 9B has adifferent planar shape. The guide groove 24 of the rack member 9Aincludes a first parallel portion 25 and a second parallel portion 26that extend substantially parallel to a longitudinal direction of therack member 9A and are displaced in a width direction of the rack member9A. The guide groove 24 of the rack member 9A also includes a diagonalportion 27 that extends diagonally with respect to the longitudinaldirection of the rack member 9A and connects the first and the secondparallel portions 25 and 26. Meanwhile, the guide groove 24 of the rackmember 9B includes a first parallel portion 28, a second parallelportion 29, and a third parallel portion 30 that extend substantiallyparallel to a longitudinal direction of the rack member 9B and areconnected by a first diagonal portion 31 and a second diagonal portion32 both extending diagonally with respect to the longitudinal directionof the rack member 9B. With the above-described structure, each of therack members 9A and 9B is integrated with each of the original documentwidth guides 7 via the connecting members 18.

By detecting a position of the pair of the movable members 10A and 10B,a position of the original document width guides 7 can be detected. Asillustrated in FIG. 6, each of the movable members 10A and 10B includesa longitudinal portion 33, which is formed of a longitudinal member, anda flat plate portion 34, which laterally protrudes from one end in thelongitudinal direction of the longitudinal portion 33. On a bottomportion of the longitudinal portion 33, a slide groove 35, which issubstantially V-shaped in its longitudinal cross-section, is formedextending in the longitudinal direction of the longitudinal portion 33.A fitting projection 36, which fits in the guide groove 24 of the rackmember 9A or 9B, protrudes from a top portion of the longitudinalportion 33. On an upper surface of the flat plate portion 34, aprojecting detection portion 37 is provided parallel to the longitudinalportion 33.

Next, a description will be made of an attachment structure of thepinion gear 8, the rack member 9B, and the movable member 10B to thereverse surface of the original document tray 6. As illustrated in FIG.6, a slide rib 38, which is substantially in an inverted V-shape in itslongitudinal cross-section in the direction that is substantiallyperpendicular to the paper feed direction 100, is provided protrudingfrom the reverse surface of the original document tray 6. The movablemember 10B can be attached movably along the slide rib 38 by fitting theslide rib 38 in the slide groove 35 formed at the bottom portion of themovable member 10B. From above the movable member 10B, the rack member9B is attached between the guide ribs 15 shown in FIG. 2 such that thefitting projection 36 of the movable member 10B fits in the guide groove24 of the rack member 9B, and the rack member 9B can slide along theguide rib 15. Accordingly, accompanying sliding movement of the originaldocument width guide 7 on the upper surface of the original documenttray 6, the rack member 9B that is integrated with the original documentguide 7 slides on the reverse surface of the original document tray 6.Moreover, as illustrated in FIG. 6, the pinion gear 8 is attached fromabove the rack member 9B. More specifically, a gear attaching boss 40with a screw hole 39 is disposed on the reverse surface of the originaldocument tray 6. The pinion gear 8 is attached such that the gearattaching boss 40 is inserted through the boss inserting hole 22, andthe teethed portion 19 meshes with the teethed portion 23 of the rackmember 9B. Upon inserting the flange 21 into the gear attaching boss 40until the flange 21 touches the rack member 9B, the pinion gear 8 can berotatably supported by screwing a screw 41 into the screw hole 39 of thegear attaching boss 40.

In the above-described structure, the pair of the original documentwidth guides 7 slides in opposite directions with respect to oneanother. In other words, when one of the original document width guides7 is slid in a direction that is substantially perpendicular to thepaper feed direction 100, the rack member 9A, which is integrated withthe original document width guide 7, slides in the direction that issubstantially perpendicular to the paper feed direction 100 as well, andthe pinion gear 8, which is meshed with the rack member 9A, startsrotating. Accordingly, the rack member 9B, which is meshed with thepinion gear 8, slides in the opposite direction of the rack member 9A,and the other original document width guide 7, which is integrated withthe rack member 9B, slides in the opposite direction of the formeroriginal document width guide 7.

Furthermore, in the above-described structure, each of the movablemembers 10A and 10B moves accompanying sliding movement of each of theoriginal document width guides 7. More specifically, when the rackmember 9B, which is integrated with the original document width guide 7,slides, the fitting projection 36 of the rack member 9B starts movingalong the guide groove 24. While the fitting projection 36 is movingalong the first parallel portion 28 of the guide groove 24, a forcetowards the paper feed direction 100 does not act upon the movablemember 10B. Therefore, only the rack member 9B slides in the directionthat is substantially perpendicular to the paper feed direction 100without moving the movable member 10B. However, when the fittingprojection 36 reaches the first diagonal portion 31 of the guide groove24, the force towards the paper feed direction 100 acts upon the movablemember 10B, and the movable member 10B starts moving along the slide rib38 in a direction towards the paper size sensor 11. The fittingprojection 36 then passes through the first diagonal portion 31, andreaches the second parallel portion 29. Accordingly, since the forcetowards the paper feed direction 100 stops acting upon the movablemember 10B, the movable member 10B stops moving. In the above-describedmanner, accompanying the sliding movement of each of the originaldocument width guides 7 in the direction that is substantiallyperpendicular to the paper feed direction 100, each of the movablemembers 10A and 10B moves in the paper feed direction 100.

The pair of the paper size sensors 11 is used to determine the papersize of the original document by detecting or not detecting each of themovable members 10A and 10B. Since a structure of the paper size sensor11 is the same as the conventional paper size sensor 82, like referencenumerals are used in FIGS. 6 and 9, and a description thereof will beomitted. As illustrated in FIG. 6, the paper size sensor 11 is attachedby fitting the snap-fits 86 of the paper size sensor 11 into a sensormounting portion 42, which is provided on the reverse side of theoriginal document tray 6, under a state in which the paper size sensor11 is lies flat, i.e., under a state in which the height direction ofthe paper size sensor 11, which is a direction in which the dimension ofthe paper size sensor 11 is large, is arranged substantially parallel tothe original document tray 6. Accordingly, the light-emitting element 83and the light-receiving element 84 face each other across a movementpath of the movable member 10B. When the projecting detection portion 37of the movable member 10B is located away from the paper size sensor 11,and light emitted from the light-emitting element 83 is being receivedby the light-receiving element 84, the paper size sensor 11 sends anON-signal to a control unit (not shown). On the other hand, while theprojecting detection portion 37 of the movable member 10B is locatedbetween the light-emitting element 83 and the light-receiving element84, and light is not being received by the light-receiving element 84,the paper size sensor 11 sends an OFF-signal to the control unit. Thus,passage or non-passage of the movable members 10A and 10B can bedetected by the paper size sensors 11.

Accordingly, the movable members 10A and 10B, which move in thedirection that is substantially perpendicular to the paper feeddirection 100, are detected by the paper size sensor 11, and the papersize sensor 11 can be attached to lie flat. In the above-describedstructure, the height of the original document tray unit 1 can bereduced as a whole compared with a structure in which the paper sizesensor 11 is attached such that the height direction of the paper sizesensor 11 extends in the height direction of the original document tray6. Therefore, the original document discharged from the paper dischargeport, which is positioned directly under the original document tray 6,can be prevented from touching the original document tray unit 1.Accordingly, since a long distance is not required to be providedbetween the paper feed port and the paper discharge port, the height ofthe ADF 3 can be reduced as a whole.

With reference to FIGS. 2 and 5, description will be made of how thesize of the original document in the paper width direction can bedetermined by the paper size sensor 11. As illustrated in FIGS. 2 and 6,for example, when each of the original document width guides 7 isadjusted to a position adjustment scale 14 indicating A3 size, themovable member 10A has the fitting projection 36 located in the firstparallel portion 25 of the rack member 9A and the projecting detectionportion 37 located between the light-emitting element 83 and thelight-receiving element 84 of the paper size sensor 11. Meanwhile, themovable member 10B has the fitting projection 36 located in the thirdparallel portion 30 of the rack member 9B and the projecting detectionportion 37 located away from both the light-emitting element 83 and thelight-receiving element 84 of the paper size sensor 11. Therefore, thecontrol unit determines that the original document placed on theoriginal document tray 6 is size A3 by receiving the OFF-signal from onepaper size sensor 11 and the ON-signal from the other paper size sensor11.

When each of the original document width guides 7 is slid from aposition illustrated in FIG. 2 towards the center of the originaldocument tray 6, each fitting projection 36 of the movable members 10Aand 10B starts moving along each guide groove 24 of the rack members 9Aand 9B respectively. As illustrated in FIG. 3, when each of the originaldocument width guides 7 is adjusted to a position adjustment scale 14indicating B4 size, the movable member 10A is stopped with the fittingprojection 36 still being located in the first parallel portion 25 ofthe rack member 9A. Accordingly, the projecting detection portion 37 islocated between the light-emitting element 83 and the light-receivingelement 84. Meanwhile, accompanying movement of the fitting projection36 of the movable member 10B from the third parallel portion 30 throughthe second diagonal portion 32 to the second parallel portion 29 of therack member 9B, the movable member 10B moves in a direction close to thepaper size sensor 11, and the projecting detection portion 37 is locatedbetween the light-emitting element 83 and the light-receiving element84. Therefore, the control unit receives an ON-signal from both papersize sensors 11, and determines that the original document placed on theoriginal document tray 6 is size B4.

When each of the original document width guides 7 is slid from aposition illustrated in FIG. 3 towards the center of the originaldocument tray 6 to be adjusted to a position adjustment scale 14indicating A4 size as illustrated in FIG. 4, the movable member 10Amoves in a direction away from the paper size sensor 11 accompanyingmovement of the fitting projection 36 from the first parallel portion 25through the diagonal portion 27 to the second parallel portion 26 of therack member 9A, and the projecting detection portion 37 moves away froma position between the light-emitting element 83 and the light-receivingelement 84. Meanwhile, the movable member 10B is stopped with thefitting projection 36 still located in the second parallel portion 29 ofthe rack member 9B, and the projecting detection portion 37 is locatedbetween the light-emitting element 83 and the light-receiving element84. Therefore, the control unit receives the ON-signal from one papersize sensor 11 and the OFF-signal from the other paper size sensor 11,and determines that the original document placed on the originaldocument tray 6 is size A4.

When each of the original document width guides 7 is slid from aposition illustrated in FIG. 4 towards the center of the originaldocument tray 6 to be adjusted to a position adjustment scale 14indicating B5 size as illustrated in FIG. 5, the fitting projection 36of the movable member 10A stays still in the second parallel portion 26of the rack member 9A, and the projecting detection portion 37 staysaway from the position between the light-emitting element 83 and thelight-receiving element 84. Meanwhile, the movable member 10B moves in adirection away from the paper size sensor 11 accompanying movement ofthe fitting projection 36 from the second parallel portion 29 throughthe first diagonal portion 31 to the first parallel portion 28 of therack member 9B, and the projecting detection portion 37 moves away fromthe position between the light-emitting element 83 and thelight-receiving element 84. Therefore, the control unit receives theOFF-signal from both paper size sensors 11, and determines that theoriginal document placed on the original document tray 6 is size B5.

In the above-described preferred embodiment, a total of four types ofpaper sizes can be determined by the two paper size sensors 11 bydetecting the passing or non-passing of the movable members 10A and 10B.However, the present invention is not limited to the above-describedpreferred embodiment. For example, based on a type of the paper size tobe used, a number of the paper size sensors 11 can be increased ordecreased, or a plan view of the slide grooves 35 formed on the rackmembers 9A and 9B can be accordingly changed.

FIG. 7 is a schematic plan view of a structure of a reverse surface ofthe original document tray unit 50 according to a second preferredembodiment of the present invention, illustrating a state in which theoriginal document width guides 7 are adjusted to the position adjustmentscale 14 indicating A4 size. Compared to the original document tray unit1 of the first preferred embodiment, the structures of rack members 51Aand 51B, and movable members 52A and 52B are different in the originaldocument tray unit 50. Since the structure of other members are the sameas the structure described in the first preferred embodiment, likereference numerals are used in FIGS. 2 and 7, and a description thereofwill be omitted. In the second preferred embodiment, instead ofproviding the guide grooves 24 on each of the rack members 51A and 51B,shaped cut-out portions 53 are respectively disposed on a side of eachof the rack members 51A and 51B opposite the side on which the teethedportion 23 is provided. Each of the cut-out portions 53 of the rackmembers 51A and 51B has a different planar shape. Meanwhile, the movablemembers 52A and 52B are blade springs that are made of meandering bentmetal plates or the like. A base end portion of each of the movablemembers 52A and 52B is attached to the reverse surface of the originaldocument tray 6, and an intermediate portion of the movable members 52Aand 52B in a longitudinal direction is respectively contacted againstthe rack members 51A and 51B. While the intermediate portion of themovable members 52A and 52B in the longitudinal direction are contactedagainst portions other than the cut-out portions 53 of the rack members51A and 51B, a leading end of the movable members 52A and 52B is locatedbetween the light-emitting element 83 and the light-receiving element 84of the paper size sensor 11. When the rack members 51A and 51B are slidand the intermediate portion of the movable members 52A and 52B in thelongitudinal direction are contacted against the cut-out portions 53,the leading end of the movable members 52A and 52B moves in a directionaway from the paper size sensor 11 and moves away from the positionbetween the light-emitting element 83 and the light-receiving element84. Therefore, the control unit receives the ON-signal from one papersize sensor 11 and the OFF-signal from the other paper size sensor 11,and determines that the original document placed on the originaldocument tray 6 is size A4. Although not illustrated in the drawings, inthe same manner as the first preferred embodiment, accompanying thesliding movement of each of the original document width guides 7, eachof the movable members 52A and 52B moves in the paper feed direction 100at different timings, and the ON/OFF-signals from the paper size sensor11 change accordingly. Accordingly, the paper size of the originaldocument placed on the original document tray 6 can be determined.

While the present invention has been described with respect to preferredembodiments thereof, it will be apparent to those skilled in the artthat the disclosed invention may be modified in numerous ways and mayassume many embodiments other than those specifically set out anddescribed above. Accordingly, the appended claims are intended to coverall modifications of the present invention that fall within the truespirit and scope of the present invention.

1. A paper tray unit comprising: a paper tray on which a paper to be fedinto a paper transportation path is placed and in which a paperdischarge port of the paper transportation path is provided directlyunder the paper tray; a paper width guide provided movably in adirection that is substantially perpendicular to a paper feed directionon an upper surface of the paper tray and arranged to position the paperin a paper width direction; a paper size sensor attached to a reversesurface of the paper tray and arranged to determine a size of the paperin the paper width direction by detecting a position of the paper widthguide; and a movable member arranged to move in the paper feed directionaccompanying the movement of the paper width guide.
 2. The paper trayunit according to claim 1, wherein a height of the paper size sensorprotruding from the reverse surface of the paper tray is within a rangein which a paper discharged from the paper discharge port does not touchthe paper size sensor.
 3. The paper tray unit according to claim 2,wherein the paper size sensor is a transmissive optical sensor whichemits a light beam across a detection groove through which the movablemember passes.
 4. The paper tray unit according to claim 3, wherein thepaper size sensor has a maximum dimension in a height direction of thedetection groove and is attached such that the height direction of thedetection groove is substantially parallel to the paper tray unit. 5.The paper tray unit according to claim 4, wherein each of the paperwidth guide, the paper size sensor, and the movable member include apair of paper width guides, a pair of paper size sensors, and a pair ofmovable members; the paper tray unit includes a pair of rack membersintegral with the pair of the paper width guides; and the pair of themovable members moves in a direction that is substantially perpendicularto a moving direction of the rack members in response to a movement ofthe rack members, and a paper size is determined by the pair of thepaper size sensors detecting a position of the movable members.
 6. Thepaper size sensor according to claim 5, wherein the pair of the paperwidth guides is integral with the pair of the rack members via arespective connecting member, and is slidable on the paper tray within arange in which the connecting member is guided along an elongated holeprovided on the paper tray.
 7. The paper tray unit according to claim 6,wherein the pair of the rack members includes a longitudinal flat platemember and a teethed portion provided at one side in a width directionof the flat plate member.
 8. The paper tray unit according to claim 7,wherein a guide groove is provided along a longitudinal direction ofeach of the rack members, each guide groove is substantiallysemicircular in a longitudinal cross-section, and each guide groove hasa different planar shape.
 9. The paper tray unit according to claim 8,wherein the guide groove of a first rack member of the pair of rackmembers includes a first parallel portion and a second parallel portionextending parallel to the longitudinal direction of the first rackmember, the first and the second parallel portions are displaced in awidth direction of the first rack member, and a diagonal portionextending diagonally in the longitudinal direction of the first rackmember is provided to connect the first parallel portion and the secondparallel portion; and the guide groove of a second rack member of thepair of rack members includes a first parallel portion, a secondparallel portion and a third parallel portion extending parallel to thelongitudinal direction of the second rack member; and a first diagonalportion and a second diagonal portion extending diagonally in thelongitudinal direction of the second rack member are provided to connectthe first parallel portion, the second parallel portion, and the thirdparallel portion.
 10. The paper tray unit according to claim 9, whereina pinion gear is rotatably supported on the reverse surface of papertray; and the pinion gear includes a gear main body and a substantiallydisk-shaped flange, the gear main body has a teethed portion formedaround a circumference of a cylinder member, the flange is provided atone end of the gear main body and protrudes in a radial direction of thegear main body, and a boss inserting hole is provided through the gearmain body and the flange.
 11. The paper tray unit according to claim 10,wherein the teethed portions of the rack members and the teethed portionof the pinion gear are meshed with each other, and when the teethedportions of the rack members and the teethed portion of the pinion gearare meshed, the pair of the paper width guides move simultaneously inopposite directions.
 12. The paper tray unit according to claim 11,wherein each of the movable members includes a longitudinal portion, aflat plate portion, a fitting projection, and a projecting detectionportion; the longitudinal portion includes a longitudinal member, theflat plate portion laterally protrudes from one end of the longitudinalportion, the fitting projection protrudes from a top portion of thelongitudinal portion and fits in the guide groove of the rack member,and the projecting detection portion is provided on an upper surface ofthe flat plate portion.
 13. The paper tray unit according to claim 12,wherein a substantially V-shaped slide groove is provided on a bottomportion of the longitudinal portion of the movable member and extends inthe longitudinal direction of the longitudinal portion.
 14. The papertray unit according to claim 13, wherein the pair of the paper sizesensors includes snap-fits arranged to fit into sensor mounting portionsprovided on the reverse surface of the paper tray.
 15. The paper trayunit according to claim 7, wherein the pair of the rack members includesa shaped cut-out portion arranged on an opposite side in the widthdirection of the flat plate member from the teethed portion.
 16. Thepaper tray according to claim 15, wherein the cut-out portion on one ofthe pair of the rack members has a different planar shape from thecut-out portion on the other of the pair of rack members.
 17. The papertray unit according to claim 16, wherein the pair of the movable membersinclude blade springs made of a bent metal plate, a base end portion ofthe movable members is attached to the reverse surface of the papertray, and an intermediate portion of each of the movable members in alongitudinal direction contacts against a respective cut-out portion ofthe pair of the rack members.
 18. The paper tray unit according to claim17, wherein a pinion gear is rotatably supported on the reverse surfaceof the paper tray, the pinion gear including: a gear main body having ateethed portion arranged around a circumference of a cylinder member; asubstantially disk-shaped flange provided at one end of the gear mainbody and protruding in a radial direction of the gear main body; and aboss inserting hole penetrating through the gear main body and theflange.
 19. The paper tray unit according to claim 18, wherein the pairof the paper width guides are arranged to move by the teethed portion ofthe flat plate member meshing with the teethed portion disposed aroundthe circumference of the cylinder member.
 20. The paper tray accordingto claim 19, wherein the pair of the paper size sensors includessnap-fits arranged to fit into sensor mounting portions provided on thereverse surface of the paper tray.